let a: string = "zs"
let b: number = 12
const c: boolean = false
let d: any = 23.529
console.log(d.toFixed(2))
let e: unknown = 56
if(typeof e==="number"){
    console.log(e.toFixed(2))
}

let f:null =null
let g:undefined=undefined
//void 、never
function add():void{
    console.log("heihei")
}
function add1():never{
    throw new Error("出错了")
}
add1()
